YKL-40 can act as an acute phase protein with a range of functions in the regulation of proliferation, migration, cellular adhesion, and differentiation and is released by a plethora of cells [32]: In the periphery, YKL-40 is expressed under physiological conditions by metamyelocytes, granulocytes, macrophages, vascular smooth muscle cells, and synovial cells and under pathological conditions by various neoplasms as well as in fibrotic areas in liver diseases or during hepatitis C infection [88]. This evidence concerns the gene CHI3L1 and hepatitis C virus infection.